1 //==- CGObjCRuntime.cpp - Interface to Shared Objective-C Runtime Features ==//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 // This abstract class defines the interface for Objective-C runtime-specific
10 // code generation. It provides some concrete helper methods for functionality
11 // shared between all (or most) of the Objective-C runtimes supported by clang.
13 //===----------------------------------------------------------------------===//
15 #include "CGObjCRuntime.h"
16 #include "CGCleanup.h"
18 #include "CGRecordLayout.h"
19 #include "CodeGenFunction.h"
20 #include "CodeGenModule.h"
21 #include "clang/AST/RecordLayout.h"
22 #include "clang/AST/StmtObjC.h"
23 #include "clang/CodeGen/CGFunctionInfo.h"
24 #include "llvm/Support/SaveAndRestore.h"
26 using namespace clang;
27 using namespace CodeGen;
29 uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM,
30 const ObjCInterfaceDecl *OID,
31 const ObjCIvarDecl *Ivar) {
32 return CGM.getContext().lookupFieldBitOffset(OID, nullptr, Ivar) /
33 CGM.getContext().getCharWidth();
36 uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM,
37 const ObjCImplementationDecl *OID,
38 const ObjCIvarDecl *Ivar) {
39 return CGM.getContext().lookupFieldBitOffset(OID->getClassInterface(), OID,
41 CGM.getContext().getCharWidth();
44 unsigned CGObjCRuntime::ComputeBitfieldBitOffset(
45 CodeGen::CodeGenModule &CGM,
46 const ObjCInterfaceDecl *ID,
47 const ObjCIvarDecl *Ivar) {
48 return CGM.getContext().lookupFieldBitOffset(ID, ID->getImplementation(),
52 LValue CGObjCRuntime::EmitValueForIvarAtOffset(CodeGen::CodeGenFunction &CGF,
53 const ObjCInterfaceDecl *OID,
54 llvm::Value *BaseValue,
55 const ObjCIvarDecl *Ivar,
56 unsigned CVRQualifiers,
57 llvm::Value *Offset) {
58 // Compute (type*) ( (char *) BaseValue + Offset)
59 QualType InterfaceTy{OID->getTypeForDecl(), 0};
60 QualType ObjectPtrTy =
61 CGF.CGM.getContext().getObjCObjectPointerType(InterfaceTy);
63 Ivar->getUsageType(ObjectPtrTy).withCVRQualifiers(CVRQualifiers);
64 llvm::Type *LTy = CGF.CGM.getTypes().ConvertTypeForMem(IvarTy);
65 llvm::Value *V = CGF.Builder.CreateBitCast(BaseValue, CGF.Int8PtrTy);
66 V = CGF.Builder.CreateInBoundsGEP(V, Offset, "add.ptr");
68 if (!Ivar->isBitField()) {
69 V = CGF.Builder.CreateBitCast(V, llvm::PointerType::getUnqual(LTy));
70 LValue LV = CGF.MakeNaturalAlignAddrLValue(V, IvarTy);
74 // We need to compute an access strategy for this bit-field. We are given the
75 // offset to the first byte in the bit-field, the sub-byte offset is taken
76 // from the original layout. We reuse the normal bit-field access strategy by
77 // treating this as an access to a struct where the bit-field is in byte 0,
78 // and adjust the containing type size as appropriate.
80 // FIXME: Note that currently we make a very conservative estimate of the
81 // alignment of the bit-field, because (a) it is not clear what guarantees the
82 // runtime makes us, and (b) we don't have a way to specify that the struct is
83 // at an alignment plus offset.
85 // Note, there is a subtle invariant here: we can only call this routine on
86 // non-synthesized ivars but we may be called for synthesized ivars. However,
87 // a synthesized ivar can never be a bit-field, so this is safe.
88 uint64_t FieldBitOffset =
89 CGF.CGM.getContext().lookupFieldBitOffset(OID, nullptr, Ivar);
90 uint64_t BitOffset = FieldBitOffset % CGF.CGM.getContext().getCharWidth();
91 uint64_t AlignmentBits = CGF.CGM.getTarget().getCharAlign();
92 uint64_t BitFieldSize = Ivar->getBitWidthValue(CGF.getContext());
93 CharUnits StorageSize = CGF.CGM.getContext().toCharUnitsFromBits(
94 llvm::alignTo(BitOffset + BitFieldSize, AlignmentBits));
95 CharUnits Alignment = CGF.CGM.getContext().toCharUnitsFromBits(AlignmentBits);
97 // Allocate a new CGBitFieldInfo object to describe this access.
99 // FIXME: This is incredibly wasteful, these should be uniqued or part of some
100 // layout object. However, this is blocked on other cleanups to the
101 // Objective-C code, so for now we just live with allocating a bunch of these
103 CGBitFieldInfo *Info = new (CGF.CGM.getContext()) CGBitFieldInfo(
104 CGBitFieldInfo::MakeInfo(CGF.CGM.getTypes(), Ivar, BitOffset, BitFieldSize,
105 CGF.CGM.getContext().toBits(StorageSize),
106 CharUnits::fromQuantity(0)));
108 Address Addr(V, Alignment);
109 Addr = CGF.Builder.CreateElementBitCast(Addr,
110 llvm::Type::getIntNTy(CGF.getLLVMContext(),
112 return LValue::MakeBitfield(Addr, *Info, IvarTy,
113 LValueBaseInfo(AlignmentSource::Decl),
118 struct CatchHandler {
119 const VarDecl *Variable;
121 llvm::BasicBlock *Block;
122 llvm::Constant *TypeInfo;
123 /// Flags used to differentiate cleanups and catchalls in Windows SEH
127 struct CallObjCEndCatch final : EHScopeStack::Cleanup {
128 CallObjCEndCatch(bool MightThrow, llvm::FunctionCallee Fn)
129 : MightThrow(MightThrow), Fn(Fn) {}
131 llvm::FunctionCallee Fn;
133 void Emit(CodeGenFunction &CGF, Flags flags) override {
135 CGF.EmitRuntimeCallOrInvoke(Fn);
137 CGF.EmitNounwindRuntimeCall(Fn);
142 void CGObjCRuntime::EmitTryCatchStmt(CodeGenFunction &CGF,
143 const ObjCAtTryStmt &S,
144 llvm::FunctionCallee beginCatchFn,
145 llvm::FunctionCallee endCatchFn,
146 llvm::FunctionCallee exceptionRethrowFn) {
147 // Jump destination for falling out of catch bodies.
148 CodeGenFunction::JumpDest Cont;
149 if (S.getNumCatchStmts())
150 Cont = CGF.getJumpDestInCurrentScope("eh.cont");
152 bool useFunclets = EHPersonality::get(CGF).usesFuncletPads();
154 CodeGenFunction::FinallyInfo FinallyInfo;
156 if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt())
157 FinallyInfo.enter(CGF, Finally->getFinallyBody(),
158 beginCatchFn, endCatchFn, exceptionRethrowFn);
160 SmallVector<CatchHandler, 8> Handlers;
163 // Enter the catch, if there is one.
164 if (S.getNumCatchStmts()) {
165 for (unsigned I = 0, N = S.getNumCatchStmts(); I != N; ++I) {
166 const ObjCAtCatchStmt *CatchStmt = S.getCatchStmt(I);
167 const VarDecl *CatchDecl = CatchStmt->getCatchParamDecl();
169 Handlers.push_back(CatchHandler());
170 CatchHandler &Handler = Handlers.back();
171 Handler.Variable = CatchDecl;
172 Handler.Body = CatchStmt->getCatchBody();
173 Handler.Block = CGF.createBasicBlock("catch");
176 // @catch(...) always matches.
178 auto catchAll = getCatchAllTypeInfo();
179 Handler.TypeInfo = catchAll.RTTI;
180 Handler.Flags = catchAll.Flags;
181 // Don't consider any other catches.
185 Handler.TypeInfo = GetEHType(CatchDecl->getType());
188 EHCatchScope *Catch = CGF.EHStack.pushCatch(Handlers.size());
189 for (unsigned I = 0, E = Handlers.size(); I != E; ++I)
190 Catch->setHandler(I, { Handlers[I].TypeInfo, Handlers[I].Flags }, Handlers[I].Block);
194 if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt()) {
195 CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true);
196 if (!CGF.CurSEHParent)
197 CGF.CurSEHParent = cast<NamedDecl>(CGF.CurFuncDecl);
198 // Outline the finally block.
199 const Stmt *FinallyBlock = Finally->getFinallyBody();
200 HelperCGF.startOutlinedSEHHelper(CGF, /*isFilter*/false, FinallyBlock);
202 // Emit the original filter expression, convert to i32, and return.
203 HelperCGF.EmitStmt(FinallyBlock);
205 HelperCGF.FinishFunction(FinallyBlock->getEndLoc());
207 llvm::Function *FinallyFunc = HelperCGF.CurFn;
210 // Push a cleanup for __finally blocks.
211 CGF.pushSEHCleanup(NormalAndEHCleanup, FinallyFunc);
215 // Emit the try body.
216 CGF.EmitStmt(S.getTryBody());
219 if (S.getNumCatchStmts())
222 // Remember where we were.
223 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP();
225 // Emit the handlers.
226 for (unsigned I = 0, E = Handlers.size(); I != E; ++I) {
227 CatchHandler &Handler = Handlers[I];
229 CGF.EmitBlock(Handler.Block);
230 llvm::CatchPadInst *CPI = nullptr;
231 SaveAndRestore<llvm::Instruction *> RestoreCurrentFuncletPad(CGF.CurrentFuncletPad);
233 if ((CPI = dyn_cast_or_null<llvm::CatchPadInst>(Handler.Block->getFirstNonPHI()))) {
234 CGF.CurrentFuncletPad = CPI;
235 CPI->setOperand(2, CGF.getExceptionSlot().getPointer());
237 llvm::Value *RawExn = CGF.getExceptionFromSlot();
240 llvm::Value *Exn = RawExn;
242 Exn = CGF.EmitNounwindRuntimeCall(beginCatchFn, RawExn, "exn.adjusted");
244 CodeGenFunction::LexicalScope cleanups(CGF, Handler.Body->getSourceRange());
247 // Add a cleanup to leave the catch.
248 bool EndCatchMightThrow = (Handler.Variable == nullptr);
250 CGF.EHStack.pushCleanup<CallObjCEndCatch>(NormalAndEHCleanup,
255 // Bind the catch parameter if it exists.
256 if (const VarDecl *CatchParam = Handler.Variable) {
257 llvm::Type *CatchType = CGF.ConvertType(CatchParam->getType());
258 llvm::Value *CastExn = CGF.Builder.CreateBitCast(Exn, CatchType);
260 CGF.EmitAutoVarDecl(*CatchParam);
261 EmitInitOfCatchParam(CGF, CastExn, CatchParam);
264 CGF.EHStack.pushCleanup<CatchRetScope>(NormalCleanup, CPI);
266 CGF.ObjCEHValueStack.push_back(Exn);
267 CGF.EmitStmt(Handler.Body);
268 CGF.ObjCEHValueStack.pop_back();
270 // Leave any cleanups associated with the catch.
271 cleanups.ForceCleanup();
273 CGF.EmitBranchThroughCleanup(Cont);
276 // Go back to the try-statement fallthrough.
277 CGF.Builder.restoreIP(SavedIP);
279 // Pop out of the finally.
280 if (!useFunclets && S.getFinallyStmt())
281 FinallyInfo.exit(CGF);
284 CGF.EmitBlock(Cont.getBlock());
287 void CGObjCRuntime::EmitInitOfCatchParam(CodeGenFunction &CGF,
289 const VarDecl *paramDecl) {
291 Address paramAddr = CGF.GetAddrOfLocalVar(paramDecl);
293 switch (paramDecl->getType().getQualifiers().getObjCLifetime()) {
294 case Qualifiers::OCL_Strong:
295 exn = CGF.EmitARCRetainNonBlock(exn);
298 case Qualifiers::OCL_None:
299 case Qualifiers::OCL_ExplicitNone:
300 case Qualifiers::OCL_Autoreleasing:
301 CGF.Builder.CreateStore(exn, paramAddr);
304 case Qualifiers::OCL_Weak:
305 CGF.EmitARCInitWeak(paramAddr, exn);
308 llvm_unreachable("invalid ownership qualifier");
312 struct CallSyncExit final : EHScopeStack::Cleanup {
313 llvm::FunctionCallee SyncExitFn;
314 llvm::Value *SyncArg;
315 CallSyncExit(llvm::FunctionCallee SyncExitFn, llvm::Value *SyncArg)
316 : SyncExitFn(SyncExitFn), SyncArg(SyncArg) {}
318 void Emit(CodeGenFunction &CGF, Flags flags) override {
319 CGF.EmitNounwindRuntimeCall(SyncExitFn, SyncArg);
324 void CGObjCRuntime::EmitAtSynchronizedStmt(CodeGenFunction &CGF,
325 const ObjCAtSynchronizedStmt &S,
326 llvm::FunctionCallee syncEnterFn,
327 llvm::FunctionCallee syncExitFn) {
328 CodeGenFunction::RunCleanupsScope cleanups(CGF);
330 // Evaluate the lock operand. This is guaranteed to dominate the
331 // ARC release and lock-release cleanups.
332 const Expr *lockExpr = S.getSynchExpr();
334 if (CGF.getLangOpts().ObjCAutoRefCount) {
335 lock = CGF.EmitARCRetainScalarExpr(lockExpr);
336 lock = CGF.EmitObjCConsumeObject(lockExpr->getType(), lock);
338 lock = CGF.EmitScalarExpr(lockExpr);
340 lock = CGF.Builder.CreateBitCast(lock, CGF.VoidPtrTy);
343 CGF.Builder.CreateCall(syncEnterFn, lock)->setDoesNotThrow();
345 // Register an all-paths cleanup to release the lock.
346 CGF.EHStack.pushCleanup<CallSyncExit>(NormalAndEHCleanup, syncExitFn, lock);
348 // Emit the body of the statement.
349 CGF.EmitStmt(S.getSynchBody());
352 /// Compute the pointer-to-function type to which a message send
353 /// should be casted in order to correctly call the given method
354 /// with the given arguments.
356 /// \param method - may be null
357 /// \param resultType - the result type to use if there's no method
358 /// \param callArgs - the actual arguments, including implicit ones
359 CGObjCRuntime::MessageSendInfo
360 CGObjCRuntime::getMessageSendInfo(const ObjCMethodDecl *method,
362 CallArgList &callArgs) {
363 // If there's a method, use information from that.
365 const CGFunctionInfo &signature =
366 CGM.getTypes().arrangeObjCMessageSendSignature(method, callArgs[0].Ty);
368 llvm::PointerType *signatureType =
369 CGM.getTypes().GetFunctionType(signature)->getPointerTo();
371 const CGFunctionInfo &signatureForCall =
372 CGM.getTypes().arrangeCall(signature, callArgs);
374 return MessageSendInfo(signatureForCall, signatureType);
377 // There's no method; just use a default CC.
378 const CGFunctionInfo &argsInfo =
379 CGM.getTypes().arrangeUnprototypedObjCMessageSend(resultType, callArgs);
381 // Derive the signature to call from that.
382 llvm::PointerType *signatureType =
383 CGM.getTypes().GetFunctionType(argsInfo)->getPointerTo();
384 return MessageSendInfo(argsInfo, signatureType);